What is the most commonly used water-soluble wax in histopathology?

In histopathology, the most commonly used water-soluble wax is Carbowax. Carbowax, also known as polyethylene glycol (PEG), is favored for certain types of tissue processing because it is hydrophilic, allowing it to easily penetrate and infiltrate tissues that are often challenging to work with, particularly those that are soft or delicate. Its solubility in water makes it particularly advantageous when dealing with specimens that require special handling or that do not tolerate traditional embedding in paraffin wax.

Unlike paraffin, which is a highly prevalent embedding medium in histology due to its excellent support for a wide range of tissue types, Carbowax offers unique benefits such as less brittleness and the ability to maintain the integrity of the tissue structure. It is particularly useful for embedding frozen sections and for techniques that require clarity and avoidance of artifacts that can occur with harder materials.

While gelatin and celloidin are also used in histological techniques for specific purposes, they do not match the versatility and prevalence of Carbowax in situations requiring a water-soluble wax. Thus, Carbowax stands out as the best answer in this context due to its widespread application and effective properties in histopathologic practices.